------------[ cut here ]------------
refcount_t: saturated; leaking memory.
WARNING: lib/refcount.c:19 at refcount_warn_saturate+0x13a/0x1d0 lib/refcount.c:19, CPU#1: syz.0.48/6130
Modules linked in:
CPU: 1 UID: 0 PID: 6130 Comm: syz.0.48 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:refcount_warn_saturate+0x13a/0x1d0 lib/refcount.c:19
Code: e0 cd be 8b e8 17 da f3 fc 90 0f 0b 90 90 eb b7 e8 fb be 31 fd c6 05 39 0d d8 0a 01 90 48 c7 c7 20 cd be 8b e8 f7 d9 f3 fc 90 <0f> 0b 90 90 eb 97 e8 db be 31 fd c6 05 1d 0d d8 0a 01 90 48 c7 c7
RSP: 0018:ffffc9000411f568 EFLAGS: 00010246
RAX: df83eb6d8e87c500 RBX: 0000000000000000 RCX: ffff8880790bbd00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
RBP: ffffc9000411f690 R08: ffff8880b87247d3 R09: 1ffff110170e48fa
R10: dffffc0000000000 R11: ffffed10170e48fb R12: ffff888025562a80
R13: 1ffff92000823ec0 R14: ffff888025562a80 R15: 0000000000000000
FS:  00007fdb5cf9a6c0(0000) GS:ffff888125fb9000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fdb5cf99f98 CR3: 00000000289ea000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __refcount_add_not_zero include/linux/refcount.h:187 [inline]
 refcount_add_not_zero include/linux/refcount.h:212 [inline]
 __vma_enter_locked+0x593/0x5d0 mm/mmap_lock.c:67
 __vma_start_write+0x23/0x140 mm/mmap_lock.c:99
 vma_start_write include/linux/mmap_lock.h:213 [inline]
 vma_merge_existing_range mm/vma.c:900 [inline]
 vma_modify+0xf62/0x1a70 mm/vma.c:1611
 vma_modify_flags_uffd+0x204/0x250 mm/vma.c:1704
 userfaultfd_clear_vma mm/userfaultfd.c:1997 [inline]
 userfaultfd_release_all+0x34c/0x5d0 mm/userfaultfd.c:2116
 userfaultfd_release+0xe7/0x1b0 fs/userfaultfd.c:887
 __fput+0x44c/0xa70 fs/file_table.c:468
 task_work_run+0x1d4/0x260 kernel/task_work.c:233
 get_signal+0x11ec/0x1340 kernel/signal.c:2807
 arch_do_signal_or_restart+0x9a/0x7a0 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:41 [inline]
 exit_to_user_mode_loop+0x87/0x4f0 kernel/entry/common.c:75
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
 do_syscall_64+0x2e9/0xfa0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fdb5c18f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fdb5cf9a038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: fffffffffffffffc RBX: 00007fdb5c3e5fa0 RCX: 00007fdb5c18f749
RDX: 0000200000000100 RSI: 00000000c028aa05 RDI: 0000000000000003
RBP: 00007fdb5c213f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdb5c3e6038 R14: 00007fdb5c3e5fa0 R15: 00007fff2e39e5c8
 </TASK>